This was already confirmed to be fixed by your friend. There is no way that it would still try to play it. I was not able to reproduce it, not even without the new check. You maybe need to restart the server and verify the gamefiles on server and client. Also check the version to be really 390 or above in game. It is written in the console.

Please post in the dupe file via valid download link.

What's the path of your GMod install? Maybe there is an issue with umlaut chars.
You may need to report it to the game developers aswell as it might be a bug with the game's API. They would need the crash report file then.

I will be on vacation for a week beginning tomorrow. So I can not respond in that time.

Hello again

Kappa had old version. It's fixed for sure.

Oh, ♥♥♥♥, he's right. I'm honoring you, thank you, Great Michak

Im glad that the bug is still effectively fixed for you. However I want to remind you guys to be more careful about checking versions before re-reporting bugs that are supposed to be already fixed in the latest version.

It can always happen that bug fixes aren't as effective as hoped. In those cases I need real evidences and/or good cooperation in unless I can reproduce it my-self. Otherwise I assume that the latest version wasn't loaded in those cases and that the bug report is invalid.

This addon is only supported in the latest version with the latest official version of the game. I require some basic understanding of GMod and especially its addon system from everyone who ask me for help. This includes the ablity to give reliable information of parameters such as version, hardware specs, last time of restart, etc if asked for. This is important for me to maintain a good level of quality for code and troubleshooting support.